General Description

The relict leopard frog (Lithobates onca, aka Rana onca) is a relatively small (>3 inches) leopard frog that is very similar in appearance to the lowland leopard frog. It cannot be reliably distinguished from the lowland leopard frog without genetic analysis; however, the two species are not known to occur together (but see note under Distribution tab for Grand Canyon).  Relict leopard frogs have a reticulate pattern on the rear of the thigh that may be fuzzy or quite bold, usually no spots on the snout, and relatively short legs. The color on the back and head ranges from light brown, tan, and dark olive-brown, to charcoal. Some frogs are green, mostly on the head. Males are less spotted, more uniform in color, and are smaller in size than the females. The call of the relict leopard frog is described as short and not as loud as the northern leopard frog.

Legal Status

In 1984 it was suggested that the relict leopard frog should be considered extinct. The last known specimen was seen in Utah in the 1950s and is believed to be extirpated in the state. It was rediscovered in 1991 in parts of its historical range (Black Canyon/Virgin River) through southern Nevada and northwestern Arizona. Seven populations of the relict leopard frog were found in three distinct areas. The relict leopard frog was listed as a candidate species in May 2004. The relict leopard frog is listed as a species of special concern in Arizona.

Taxonomy

The first relict leopard frog specimen, a single adult female, was collected in 1872 in the Virgin River near the vicinity of St. George, Washington County, Utah. The relict leopard frog was first described in 1875 and subsequent reports and museum specimens provide evidence that this species had a relatively restricted range along portions of the Virgin, Muddy, and Colorado rivers, particularly in small springs that fed into those major drainages. The relict leopard frog is a true frog (family Ranidae) in the Lithobates pipiens complex (leopard frogs).

Reproduction

The relict leopard frog breeds in January through April, with peak egg laying occurring in February and March. Signs of egg laying have also been reported in November. The relict leopard frog deposits egg masses in clusters of up to 250 eggs. Males reach reproductive maturity at 1.65 inches (42 mm) in length measured from snout to vent. Conditions have been created that allowed the relict leopard frog to breed in captivity. The life history of the relict leopard frog, especially in regards to breeding and feeding habits, has not been extensively studied and much is unknown.

Diet

Adults are invertivorous, feeding on insects, spiders, crustaceans, and vertebrates. Larvae are herbivorous feeding on algae, organic debris, and plant tissue.

Threats

The relict leopard frog has declined across its range and is vulnerable to extinction. Its total population size is small. Dispersal among the remaining habitats has been reduced by the formation of Lake Mead. Probable causes for the decline include loss or alteration of aquatic habitat for agriculture, urban and water development, degradation of habitat by cattle and wild burro grazing, emergent vegetation encroachment, and competition with non-native species (bullfrogs, non-native fish, crayfish, and western spiny soft-shell turtle). Water development has flooded historical habitat, eliminated brief annual floods that would prevent the encroachment of emergent vegetation, and eliminated connectivity between remaining populations. Extensive grazing can cause habitat degradation, although in some situations managed grazing of emergent vegetation may benefit the relict leopard frog by providing open water habitats. Threats also include non-native species, population fragmentation, small population size, low genetic variation, encroachment of emergent vegetation, right of way impacts, natural erosion, and recreational impacts.

More Information

Additional information on this species, as well as source documentation, can be found in the species accounts located at this link (PDF). Technical Reports on this species can be found here.

Updated December 30, 2016

Relict leopard frogs historically occurred within the Virgin River drainage downstream from the vicinity of Hurricane, Utah, along the Muddy River drainage in Nevada, and along the Colorado River from its confluence with the Virgin River downstream to the Black Canyon area below Lake Mead, Nevada and Arizona.

The image below shows the distribution range of the Relict Leopard Frog.

Extant populations of Rana onca were detected at seven sites in three distinct areas during the 1990s:

• Overton Arm of Lake Mead, Clark County, Nevada
  • Blue Point, Rogers, and Corral springs
• Black Canyon near the Colorado River below Lake Mead, in Clark County, Nevada
  • Boy Scout, Salt Cedar, and Bighorn Sheep springs
• Adjacent to the Virgin River four kilometers northeast of Littlefield, in Mohave Country, Arizona
  • Reber Spring

The populations at Corral and Reber springs were extirpated in 1995 and 1998, respectively. Probable causes for these extirpations were emergent vegetation encroachment and the presence of American bullfrogs. It was estimated that the total number of frogs at all sites, based on mark-recapture data, visual encounter studies (VESs), and extent of habitat was 1,100 frogs. The U.S. Fish and Wildlife Service (USFWS) estimated that the current distribution is less than 20% of the historical distribution.

The relict leopard frog inhabits permanent streams, springs, and spring-fed wetlands below 720 m in elevation that have constant water temperatures between 16 and 55°C. Historic habitat included sites with some submerged, emergent, or perimeter vegetation that supports an adequate amount of food resources. Habitat must have adequate variability to provide cover and egg laying sites and be free of nonnative predators.

Relict leopard frog historical habitat is described as sites with permanent cold water and stream pools that are 12 to 16 inches (30-40 cm) deep. The five sites currently inhabited by relict leopard frogs are characterized by spring systems with largely unaltered hydrology and no introduced American bull frogs or game fishes. Excessive emergent vegetation of native and non-native species is believed to be a threat to relict leopard frogs. Adults have been observed preferring relatively open shorelines where dense vegetation does not dominate.

LCR MSCP Conservation Measures

The Habitat Conservation Plan provides conservation measures specific to each species. Listed below are the species specific conservation measures for the relict leopard frog. Click on the arrows to expand the table.

The LCR MSCP provided a total of $100,000 to the National Park Service through Work Task C4 to support relict leopard frog (Lithobates onca) research and conservation. Funding for this research was initiated in 2005 and continued through 2015. The final funding was provided to the National Park Service on March 30, 2015.

This funding helped augment the National Park Service budget so additional research and monitoring of relict leopard frogs could be conducted that otherwise would not have been possible. This included monitoring historical sites where relict leopard frogs are found, the rearing, translocation, and augmentation of frogs and tadpoles to suitable but unoccupied habitat within their historic range as well as researching additional areas with the potential to provide suitable habitat for translocation.

Research and Monitoring Activities

The LCR MSCP conducts a variety of research and monitoring activities along the LCR encompassing both MSCP and non-MSCP species. For a complete list of all activities, please see the Research and Monitoring Activities web page.

This gallery includes photos of this species. If you require larger photos, please contact our webmaster Michelle Reilly at mreilly@usbr.gov.